Girentuximab is an antibody against Carbonic Anhydrase IX (CAIX), an antigen that is expressed on the cell surface of 95% of clear cell RCC (ccRCC). Zr-89-girentuximab PET/CT (Positron Emission Tomography) may be a valuable imaging technique in the diagnosis of patients with RCC. The aim of the present study is to show the impact of the Zr-89-girentuximab PET/CT on the clinical management of ccRCC patients.

More advanced imaging methods are needed to reliably distinguish benign small renal masses (SRM) from renal cell carcinoma (RCC) to prevent invasive biopsies or unnecessary surgery. Similarly, improved imaging methods are needed for unambiguous detection of lesions suspect for metastatic and relapse RCC during follow-up. Girentuximab is an antibody against Carbonic Anhydrase IX (CAIX), an antigen that is expressed on the cell surface of 95% of clear cell RCC (ccRCC). Zr-89-girentuximab PET/CT may be a valuable imaging technique in the diagnosis of patients with RCC. The aim of the present study is to show the impact of the Zr-89-girentuximab PET/CT on the clinical management of ccRCC patients. Thirty patients will be included in whom conventional diagnostics are inconclusive. During a multidisciplinary team (MDT) the hypothetical next step in the clinical process will be noted (e.g. further diagnostics, treatment or active surveillance). Subsequently, in these patients a Zirconium-89-girentuximab PET/CT will be performed. Patients will receive a single intravenous dose of 5 mg Zirconium-89-girentuximab (37 MBq). A PET/CT scan will be acquired 4 or 5 days after injection. The Zirconium-89-girentuximab PET/CT will be read by a clinician with extensive experience in radiolabeled girentuximab imaging. The results of the PET/CT will be discussed during the MDT and will be used to decide what the next step in the clinical process will be. This step will be compared with the hypothetical next step from the MDT before the scan.

Inclusion Criteria:

In order to participate in this study, a subject must meet all of the following criteria:

1. His or her clinician should face a diagnostic dilemma; e.g.

   • patients with a renal mass of unknown origin, or
   • patients with a primary renal mass in whom it is unclear whether there is metastatic disease, or
   • patients with a history of clear cell RCC with a suspicion of relapse or metastatic disease.

2. Minimum age 18 years

3. Signed informed consent

Exclusion Criteria:

• History of a CAIX-negative or non clear cell RCC.
• Administration of tyrosine kinase inhibiters within 1 month prior to inclusion.
• Any medical condition present that in the opinion of the investigator will affect patients' clinical status. - Administration of a radioisotope within 10 physical half lives prior to study enrollment
• Pregnancy or lactation.
• Known hypersensitivity or HACA (human anti chimeric antibodies) against Girentuximab.

Data will be published anonymously